(1) Field of the Invention
This invention relates to a monitor wafer and method used to monitor the use of clamp ring shielding tabs to preserve alignment marks by shielding the alignment marks during deposition of material on a wafer.
(2) Description of the Related Art
The preservation of alignment marks after the deposition of layers of material on a wafer is of primary importance in photolithographic processing of integrated circuit wafers. One method used to preserve the alignment marks is to place shielding tabs on the clamp rings used to hold the wafer in place during material deposition. The effectiveness of the shielding tabs depends on the location of the shielding tabs when material is deposited, and continual monitoring of this location is important.
U.S. Pat. No. 5,456,756 to Ramaswami et al. and U.S. Pat. No. 5,614,446 to Ramaswami et al. describes the use of shielding tabs on the clamp ring used to hold wafers in place during material deposition to shield the alignment marks during material deposition. This shielding prevents material from being deposited over the alignment marks and obscuring the alignment marks.
U.S. Pat. No. 5,320,728 to Tepman describes a planar magnetron sputtering source used to produce a uniform coating of material during material deposition on a wafer.